Magnetic recording head and disk drive provided therewith

ABSTRACT

According to one embodiment, a magnetic recording head includes a main pole configured to apply a recording magnetic field to a recording layer of a recording medium, a trailing shield opposed to the main pole with a write gap therebetween, and a high-frequency oscillator between the main pole and the trailing shield in a range of a width of the main pole in a track width direction, and configured to generate a high-frequency magnetic field. The high-frequency oscillator includes a spin injection layer, an intermediate layer, and an oscillation layer, and at least the oscillation layer comprises divided oscillation regions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2011-187567, filed Aug. 30, 2011;the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a magnetic recordinghead for perpendicular magnetic recording used in a disk drive and to adisk drive provided with this magnetic recording head.

BACKGROUND

A disk drive, such as a magnetic disk drive, comprises a magnetic disk,spindle motor, magnetic head, and carriage assembly. The magnetic diskis disposed in a case. The spindle motor supports and rotates themagnetic disk. The magnetic head reads data from and writes data to themagnetic disk. The carriage assembly supports the magnetic head formovement relative to the magnetic disk. A head section of the magnetichead comprises a recording head for writing and a read head for reading.

Magnetic heads for perpendicular magnetic recording have recently beenproposed in order to increase the recording density and capacity of amagnetic disk drive or reduce its size. In one such magnetic head, arecording head comprises a main pole configured to produce aperpendicular magnetic field, return pole or write shield pole, andcoil. The return pole or write shield pole is located on the trailingside of the main pole with a write gap therebetween and configured toclose a magnetic path that leads to a magnetic disk. The coil serves topass magnetic flux through the main pole.

For the purpose of improving recording density, there is suggested amagnetic recording head adopting a high-frequency magnetic field assistrecording system wherein a spin-torque oscillator is provided as ahigh-frequency oscillation element between a main pole and a return poleand a high-frequency magnetic field is applied to the magnetic recordinglayer from this spin-torque oscillator.

When using as the spin-torque oscillator an oscillator whose elementsize is as large as a dimension of the main pole in a track widthdirection, circularly-polarized high-frequency magnetic field intensity(c-Hac) of 410 (Oe) can be generated in a perpendicular magneticrecording layer if oscillation is excellently performed, but theoscillation is not excellently effected in reality, and oscillation ofonly approximately 180 (Oe) is carried out. It is considered that such astate occurs because a spin wave is excited on an oscillation layer ofthe spin-torque oscillator and energy is considerably lost. Further,since excitation of the spin wave is suppressed when the element size isreduced, the oscillation is excellent, but produced high-frequencymagnetic field intensity is insufficient, and excellent high-frequencyassist recording is difficult.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a hard disk drive (referred to asan HDD hereinafter) according to a first embodiment;

FIG. 2 is a side view showing a magnetic head and a suspension in theHDD;

FIG. 3 is a cross-sectional view showing a head unit of the magnetichead in an enlarging manner;

FIG. 4 is a perspective view schematically showing a recording head anda reproducing head;

FIG. 5 is a perspective view showing a main pole end portion and aspin-torque oscillator of the recording head;

FIG. 6 is a cross-sectional view showing an end portion of the recordinghead on a magnetic disk side in an enlarging manner;

FIG. 7 is a view showing a relationship between circularly-polarizedhigh-frequency magnetic field intensity (c-Hac) generated from thespin-torque oscillator and a shape and a dimension of the spin-torqueoscillator;

FIG. 8A, FIG. 8B, and FIG. 8C are perspective views showing spin-torqueoscillators according to first, second, and third modifications,respectively;

FIG. 9A, FIG. 9B, and FIG. 9C are perspective views showing spin-torqueoscillators according to fourth, fifth, and sixth modifications;

FIG. 10 is a perspective view showing a spin-torque oscillator accordingto a seventh modification;

FIG. 11 is a perspective view showing a main pole end portion and aspin-torque oscillator of a recording head in an HDD according to asecond embodiment;

FIG. 12 is a view showing a relationship between circularly-polarizedhigh-frequency magnetic field intensity (c-Hac) generated from thespin-torque oscillator and a shape and a dimension of the spin-torqueoscillator according to the second embodiment;

FIG. 13 is a perspective view showing a main pole end portion and aspin-torque oscillator of a recording head in an HDD according to athird embodiment; and

FIG. 14 is a plan view schematically showing a mask used when processingan oscillation layer of the spin-torque oscillator in the thirdembodiment.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings. In general, according to one embodiment, amagnetic recording head comprises: a main pole configured to apply arecording magnetic field to a recording layer of a recording medium; atrailing shield opposed to the main pole with a write gap therebetween;and a high-frequency oscillator between the main pole and the trailingshield in a range of a width of the main pole in a track widthdirection, and configured to generate a high-frequency magnetic field.The high-frequency oscillator comprises a spin injection layer, anintermediate layer, and an oscillation layer, and at least theoscillation layer comprises divided oscillation regions.

First Embodiment

FIG. 1 shows an internal configuration of an HDD as a disk driveaccording to a first embodiment with a top cover being removed, and FIG.2 shows a magnetic head in a flying state. As shown in FIG. 1, the HDDcomprises a housing 10. This housing 10 comprises an open-toppedrectangular box-shaped base 11 and a non-illustrated rectangular tabulartop cover. The top cover is screwed to the base using screws to close anupper end opening of the base. As a result, the inside of the housing 10is air-tightly maintained and can communicate with outside forventilation through a breather filter 26 alone.

A magnetic disk 12 as a recording medium and a drive unit are providedon the base 11. The drive unit comprises a spindle motor 13 thatsupports and rotates the magnetic disk 12, a plurality of (e.g., two)magnetic heads 33 that record and reproduce data on and from the disk12, a head actuator 14 that supports these magnetic heads 33 formovement relative to the surfaces of the magnetic disk 12, and a voicecoil motor (which will be referred to as a VCM hereinafter) 16 thatrotationally moves and positions the head actuator. Further, on the base11 are provided a ramp loading mechanism 18 that holds the magneticheads 33 in a position off the magnetic disk 12 when the magnetic heads33 are moved to the outermost periphery of the magnetic disk 12, aninertia latch 20 that holds the head actuator 14 in a retracted positionif the HDD is jolted, for example, and a board unit 17 having electroniccomponents such as a preamplifier, a head IC, and others mountedthereon.

A control circuit board 25 is attached to the outer surface of the base11 by screws such that it faces a bottom wall of the base 11. Thecontrol circuit board 25 controls the operations of the spindle motor13, the VCM 16, and the magnetic heads 33 through the board unit 17.

As shown in FIG. 1 and FIG. 2, the magnetic disk 12 is constituted as aperpendicular magnetic recording medium. The magnetic disk 12 is formedinto a discoid shape having a diameter of, e.g., approximately 2.5inches and has a board 19 made of a non-magnetic material. On eachsurface of the board 19 are sequentially laminated a soft magnetic layer23 as an underlying layer and a perpendicular magnetic recording layer22 having magnetic anisotropy in a direction perpendicular to the disksurface, and a protective film 24 is further formed thereon.

As shown in FIG. 1, the magnetic disk 12 is coaxially fitted on a hub ofthe spindle motor 13, clamped by a clamp spring 21 screwed at an upperend of the hub, and thereby fixed to the hub. The magnetic disk 12 isrotated in a direction of an arrow B at a predetermined speed by thespindle motor 13 as a drive motor.

The head actuator 14 comprises a bearing portion 15 fixed on a bottomwall of the base 11 and arms 27 extended from the bearing portion. Thesearms 27 are placed at predetermined intervals therebetween in parallelwith the surface of the magnetic disk 12, and they are extended in thesame direction from the bearing portion 15. The head actuator 14includes an elastically deformable elongated plate-shaped suspension 30.A suspension 30 is constituted of a leaf spring, and its proximal end isfixed to an end of each arm 27 by spot welding or bonding and extendedfrom each arm. The magnetic head 33 is supported at an extended end ofeach suspension 30 through a gimbal spring 41. The suspension 30, thegimbal spring 41, and the magnetic head 33 constitute a head gimbalassembly. It is to be noted that the head actuator 14 may be configuredto comprise a so-called E block in which a sleeve of the bearing portion15 and the arms are integrally formed.

As shown in FIG. 2, each magnetic head 33 has a slider 42 formed into asubstantially rectangular parallelepiped shape and arecording/reproduction head portion 44 provided at an outflow end (atrailing end) of this slider. A head load L heading for the surface ofthe magnetic disk 12 is applied to each magnetic head 33 by elasticityof the suspension 30. Two arms 27 are placed in parallel at apredetermined interval therebetween, and the suspension 30 and themagnetic head 33 disposed to each of these arms face the counterparts tosandwich the magnetic disk 12 therebetween.

Each magnetic head 33 is electrically connected to a later-describedmain FPC 38 through a relay flexible printed circuit board (referred toas a relay FPC hereinafter) 35 fixed on the suspension 30 and the arm27.

As shown in FIG. 1, the board unit 17 has an FPC main body 36 formed ofa flexible printed circuit board and a main FPC 38 extended from thisFPC main body. The FPC main body 36 is fixed on the bottom surface ofthe base 11. Electronic components including a preamplifier 37, a headIC, and others are mounted on the FPC main body 36. An extended end ofthe main FPC 38 is connected to the head actuator 14, and it isconnected to the magnetic head 33 through each relay FPC 35.

The VCM 16 has a non-illustrated support frame extended from the bearingportion 15 in an opposite direction of the arm 27 and a voice coilsupported by the support frame. In a state that the head actuator 14 isincorporated in the base 11, the voice coil is placed between a pair ofyokes 34 fixed on the base 11, and the voice coil, these yokes, andmagnets fixed to the yokes constitute the VCM 16.

In a state that the magnetic disk 12 is rotated, when the voice coil ofthe VCM 16 is energized, the head actuator 14 rotationally moves, andthe magnetic head 33 is moved onto and positioned on a desired track ofthe magnetic disk 12. At this time, the magnetic head 33 is movedbetween an inner peripheral portion and an outer peripheral portion ofthe magnetic disk along a radial direction of the magnetic disk 12.

A configuration of the magnetic head 33 will now be described in detail.FIG. 3 is an enlarged cross-sectional view showing the head portion 44of the magnetic head 33, FIG. 4 is a perspective view schematicallyshowing a recording head and a reproducing head, FIG. 5 is an enlargedcross-sectional view showing an end portion of the recording head on themagnetic disk side, and FIG. 6 is a layout plan showing the recordinghead portion from an ABS surface side of the slider.

As shown in FIG. 2 and FIG. 3, the magnetic head 33 is constituted as afloat type head and has a slider 42 formed into a substantiallyrectangular parallelepiped shape and a head portion 44 formed at an endportion of the slider on an outflow end (trailing) side. The slider 42is formed of, e.g., a sintered compact (AlTiC) of alumina and a titaniumcarbide, and the head portion 44 is formed by laminating a thin film.

The slider 42 has a rectangular disk facing surface (an air bearingsurface (ABS)) facing the surface of the magnetic disk 12. The slider 42is maintained in a state that it floats to a predetermined height fromthe magnetic disk surface by an air current C generated between the disksurface and the disk facing surface 43 due to rotation of the magneticdisk 12. A direction of the air current C coincides with a rotationaldirection B of the magnetic disk 12. The slider 42 is arranged withrespect to the surface of the magnetic disk 12 in such a manner that alongitudinal direction of the disk facing surface 43 substantiallycoincides with the direction of the air current C.

The slider 42 has a leading end 42 a placed on an inflow side of the aircurrent C and a trailing end 42 b placed on an outflow side of the aircurrent C. A leading step, a trailing step, a side step, a negativepressure cavity, and others which are not shown in the drawings areformed on the disk facing surface 43 of the slider 42.

As shown in FIG. 3 and FIG. 4, the head portion 44 has a reproducinghead 54 and a recording head 56 formed at the trailing end 42 b of theslider 42 in a thin-film process, and it is formed as a separation typemagnetic head.

The reproducing head 54 is constituted of a magnetic film 50 whichexercises a magneto-resistance effect and shield films 52 a and 52 bwhich are arranged on a trailing side and a leading side of thismagnetic film to sandwich the magnetic film 50. The magnetic film 50 andlower ends of the shield films 52 a and 52 b are exposed on the diskfacing surface 43 of the slider 42.

The recording head 56 is provided on the trailing end 42 b side of theslider 42 with respect to the reproducing head 54. The recording head 56has a main pole 66 made of a high magnetic permeability material whichgenerates a recording magnetic field in a direction perpendicular to thesurface of the magnetic disk 12, a trailing shield 62 (a return pole) 68which is arranged on the trailing side of the main pole 66 and providedto efficiently close a magnetic path through the soft magnetic layer 23immediately below the main pole, and a recording coil 71 which isarranged to wind around a magnetic path including the main pole 66 andthe trailing shield 68 in order to flow a magnetic flux through the mainpole 66 when writing a signal into the magnetic disk 12.

A power supply 70 is connected to the main pole 66 and the trailingshield 68, and a current circuit is constituted so that a current can beconducted from this power supply through the main pole 66 and thetrailing shield 68 in series.

As shown in FIG. 3 to FIG. 6, the main pole 66 substantiallyperpendicularly extends with respect to the surface of the magnetic disk12. An end portion 66 a of the main pole 66 on the magnetic disk 12 sideis narrowed to taper toward the disk surface. The end portion 66 a ofthe main pole 66 has a cross section formed into, e.g., a rectangularshape, and an end surface of the main pole 66 is exposed on the diskfacing surface 43 of the slider 42. In this embodiment, a width of theend portion 66 a of the main pole 66 substantially corresponds to awidth of the track of the magnetic disk 12.

The trailing shield 68 is formed into a substantially U-like shape, andits end portion 68 a is formed into an elongated rectangular shape. Anend surface of the trailing shield 68 is exposed on the disk facingsurface 43 of the slider 42. A leading side end surface 68 b of the endportion 68 a extends along the width direction of each track of themagnetic disk 12. This leading side end surface 68 b faces a trailingside end surface 67 a of the main pole 60 in parallel to interpose awrite gap WG therebetween.

The recording head 56 includes a high-frequency oscillator, e.g., aspin-torque oscillator 74 provided between the end portion 66 a of themain pole 66 and the trailing shield 68. The spin-torque oscillator 74is sandwiched between the trailing side end surface 67 a of the endportion 66 a of the main pole 66 and the leading side end surface 68 bof the trailing shield 68, and it is arranged in parallel to endsurfaces of these members. That is, the spin-torque oscillator 74 isplaced in the range of the width of the main pole end portion along thetrack width direction in the write gap WG and arranged at a positionincluding a center line of the main pole 66.

The spin-torque oscillator 74 has an end exposed on the ABS surface andit is provided at the same height position as the end surface of themain pole 66 with respect to the surface of the magnetic disk 12. When avoltage is applied to the main pole 66 and the trailing shield 68 fromthe power supply 70 under control of the control circuit board 25,direct-current electricity is applied to the spin-torque oscillator 74in a film thickness direction. When energization is performed,magnetization of an oscillation layer in the spin-torque oscillator 74is rotated, thereby generating a high-frequency magnetic field. As aresult, the high-frequency magnetic field is applied to the recordinglayer of the magnetic disk 12. In this manner, the trailing shield 68and the main pole 66 function as an electrode that perpendicularlyenergizes the spin-torque oscillator 74.

As shown in FIG. 3 and FIG. 4, the trailing shield 68 has a couplingportion 65 which is close to the upper portion of the main pole 66 inthe write gap WG, i.e., at a position apart from the disk facing surfaceof the slider. This coupling portion 65 is coupled with the main pole 66through a back gap portion 67 formed of an insulator such as SiO₂. Thisinsulator achieves electrical insulation of the main pole 66 and thetrailing shield 68. When the back gap portion 67 is made of theinsulator in this manner, a current can be efficiently applied to thespin-torque oscillator 74 from the power supply 70 through the main pole66 and the trailing shield 68 which also serve as the electrode of thespin-torque oscillator 74. As the insulator of the back gap portion 67,it is possible to use Al₂O₃ besides SiO₂.

The back gap portion 67 may be made of a semiconductor such as Si or Ge.An electrical conductor may be contained in a part of the back gapportion 67 made of the insulator or the semiconductor to electricallyconnect the main pole 66 to the trailing shield 68. When such aconfiguration is adopted, since electrostatic discharge during a processtreatment occurs through the back gap portion 67, the spin-torqueoscillator 74 can be prevented from being damaged during themanufacturing process, thereby improving a process yield. Further, asufficient current can be applied to the spin-torque oscillator 74 bysetting electrical resistance in the back gap portion 67 to be equal toor above electrical resistance in the spin-torque oscillator 74.

As shown in FIG. 5 and FIG. 6, the spin-torque oscillator 74 isconstituted by sequentially laminating from the main pole 66 side towardthe trailing shield 68 side, e.g., an underlying layer 74 a formed of aTa/Ru laminated film, a spin-injection layer (a second magnetic materiallayer) 74 b formed of an artificial lattice film with a film thicknessof 12 nm obtained by laminating Co/Ni 15 times, a Cu intermediate layer74 c with a film thickness of 2 nm, an oscillation layer (a firstmagnetic material layer) 74 d formed of an FeCoAl magnetic film with afilm thickness of 15 nm, and a cap layer 74 e formed of a Cu/Rulaminated film. Furthermore, the underlying layer 74 a and the cap layer74 e are connected to the main pole 66 and the trailing shield 68 whichalso serve as the electrode, respectively. It is preferable for a lengthWT2 of the spin-torque oscillator 74 in the track width direction to beequal to or smaller than a length WT1 of the trailing side end surface67 a of the main pole 66 in the track width direction.

Coercive force of the oscillation layer 74 d is smaller than a magneticfield applied from the main pole 66, and coercive force of the spininjection layer 74 b is smaller than a magnetic field applied from themain pole 66.

A soft magnetic material is desirable as a material of the oscillationlayer 74 d, there is used an alloy containing at least one of Ni, Fe,and Co such as NiFe, FeCoSi, FeNiCo, CoFe, or FeSi besides FeCoAl, anartificial lattice magnetic layer obtained by laminating an alloycontaining at least one of Ni, Fe, and Co such as FeCo/Ni, Fe/Ni, orFe/Co, or a Whistler alloy such as CoMnSi, CoFeMnSi, CoFeAlSi, CoMnAl,CoMnGaSn, CoMnGaGe, CoCrFeSi, or CoFeCrAl.

A material having perpendicular magnetic anisotropy is desirable as amaterial of the spin injection layer 74 b, and it is possible toappropriately use a material superior in perpendicular magneticanisotropy, e.g., a CoCr-based magnetic layer such as CoCrPt, CoCrTa,CoCrTaPt, or CoCrTaNb, or an RE-TM-based amorphous alloy magnetic layersuch as TbFeCo, an artificial lattice magnetic layer of a Co alloy andan alloy using a platinum group element, e.g., Pd, Pt, or Ni such asCo/Pd, Co/Pt, CoCrTa/Pd, Co/Ni, or Co/NiPt, a CoPt-based or FePt-basedalloy magnetic layer, or an SmCo-based alloy magnetic layer.

Moreover, the oscillation layer 74 d may have a configuration obtainedby laminating a soft magnetic material and a perpendicular magneticanisotropic material used for the spin injection layer. Adopting thisconfiguration enables adjusting the perpendicular magnetic anisotropy ofthe evened oscillation layer, thereby realizing optimum oscillation.

The spin injection layer 74 b may be formed by laminating a materialhaving high spin polarizability on an interface between itself and theintermediate layer 74 c. For example, it is possible to adopt aconfiguration obtained by laminating an FeCo-based alloy such as FeCo orFeCoAl, a Whistler alloy such as CoMnSi, CoFeMnSi, CoFeAlSi, CoMnAl,CoMnGaSn, CoMnGaGe, CoCrFeSi, or CoFeCrAl, and a material havingperpendicular magnetic anisotropy. Using this configuration enablesimproving spin-torque efficiency from the spin injection layer 74 b,which is advantages to reduction of an applied current density.

A material having a long spin diffusion length is desirable as amaterial of the intermediate layer 74 c, and it is possible to use anoble metal such as Cu, Pt, Au, Ag, Pd, or Ru or a non-magnetictransition metal such as Cr, Rh, Mo, or W. Additionally, theintermediate layer 74 c may have a current confining structure made ofan alumina base material and Cu or of an alumina base material and anNiFe alloy.

It is desirable to set an element size (a size of a cross sectioncutting across a plane perpendicular to a laminating direction) of thespin-torque oscillator 74 to a 10-nm square to a 100-nm square. Anelement shape is not restricted to a rectangular parallelepiped shape,and a cylindrical shape or a hexagonal columnar shape may be adopted.However, materials used for the oscillation layer 74 d, the spininjection layer 74 b, and the intermediate layer 74 c and sizes of theselayers can be arbitrarily selected without being restricted theabove-described size.

It is to be noted that the spin injection layer 74 b, the intermediatelayer 74 c, and the oscillation layer 74 d are sequentially laminated,but the oscillation layer, the intermediate layer, and the spininjection layer may be laminated in the mentioned order. In this case, adistance between the main pole 66 and the oscillation layer 74 d isreduced, and the range that a recording magnetic field generated by themain pole 66 is efficiently superimposed on a high-frequency magneticfield generated by the oscillation layer is widened on the medium,thereby enabling excellent recording.

In this embodiment, the oscillation layer 74 d of the spin-torqueoscillator 74 is segmented or divided into a plurality of oscillationregions. Fore example, a slit 80 (or a notch) having a depth equal tothe film thickness of the oscillation layer 74 d is formed at asubstantially central part of the oscillation layer 74 d, and this slit80 extends in parallel to the surface of the magnetic disk 12. This slit80 divides the oscillation layer 74 d into two oscillation regions 82 aand 82 b aligned along a direction perpendicular to the surface of themagnetic disk 12 to interpose a gap therebetween.

The slit 80 or the notch is formed by performing etching to remove theoscillation layer from the surface side of the oscillation layer basedon, e.g., ion milling or RIE after film formation of the oscillationlayer 74 d. After forming the slit 80 or the notch, it is filled with,e.g., the cap layer 74 e. Further, it may be filled with an insulatorsuch as SiO2 or Al2O3 or a semiconductor such as Si or Ge. When the slit80 or the notch is filled with such an insulator or semiconductor, acurrent is concentrated on the oscillation regions 82 a and 82 b, thuseffecting oscillation with a lower voltage. It is to be noted that theslit 80 or the notch is not restricted to the strip-like shape, and itmay be formed into a bent or crossed shape or a shape that is not openedto a side edge of the oscillation layer.

When the oscillation layer 74 d of the spin-torque oscillator 74 isdivided into oscillation regions in this manner, the spin-torqueoscillator 74 can oscillate with a lower driving voltage, and it canalso oscillate with a large amplitude, thereby increasing a generatedhigh-frequency magnetic field. When the sufficient high-frequencymagnetic field is generated, the sufficient recording capability can beexercised, and stable recording characteristics can be realized.

FIG. 7 shows a relationship between circularly-polarized high-frequencymagnetic field intensity (c-Hac) generated from the spin-torqueoscillator and a shape and a dimension of the spin-torque oscillator.When the spin-torque oscillator 74 having an element size of 50 nm×50 nmis created, c-Hac of 410 (Oe) can be produced if excellent oscillationis carried out, but oscillation of approximately 180 (Oe) is actuallydifficult. It can be considered the oscillation is difficult because aspin wave is excited on the oscillation layer 74 d and energy is greatlylost. Further, since an element having an element size of 50 nm×17 nm issmall in element size, the excitation of a spin wave is suppressed, andhence the oscillation becomes excellent. However, since the element sizeis small, the generated c-Hac is just 290 (Oe).

In this embodiment, since the oscillation layer 74 d is divided into theoscillation regions 81 a and 82 b, it is equivalent to a configurationhaving two elements each having a size of 50 nm×17 nm on upper and lowersides, and the generated c-Hac becomes 330 (Oe) as shown in FIG. 7.Therefore, according to this embodiment, it can be understood that anoscillation amplitude of the oscillation layer 74 d can be increasedwith a lower driving voltage and the circularly-polarized high-frequencymagnetic field intensity generated from the spin-torque oscillator 74 israised. As a result, good high-frequency assist recording is enabled. Itis to be noted that the generated c-Hac is a value measured on themagnetic disk surface immediately below the spin-torque oscillator 74.

According to the thus-configured HDD, when the VCM 16 is driven, thehead actuator 14 is rotationally moved, and the magnetic head 33 ismoved onto and positioned on a desired track of the magnetic disk 12.Further, the magnetic head 33 floats by an air current C generatedbetween the disk surface and the disk facing surface 43 by the rotationof the magnetic disk 12. At the time of operations of the HDD, the diskfacing surface 43 of the slider 42 faces the disk surface while keepinga gap therebetween. As shown in FIG. 2, the magnetic head 33 floats inan inclined posture that enables the closet approach of recording head56 of the head portion 44 to the surface of the magnetic disk 12. Inthis state, the reproducing head 54 is used to read recorded informationfrom the magnetic disk 12, and the recording head 56 is used to writeinformation into the magnetic disk 12.

In writing of information, direct-current electricity is flowed throughthe spin-torque oscillator 74 to generate a high-frequency magneticfield, and this high-frequency magnetic field is applied to theperpendicular magnetic recording layer 22 of the magnetic disk 12.Further, when the recording coil 71 excites the main pole 66 and thismain pole applies a perpendicular recording magnetic field to therecording layer 22 of the magnetic disk 12 provided immediately below,information is recorded with a desired track width. When thehigh-frequency magnetic field is superimposed on the recording magneticfield, magnetic recording with high retaining force and high magneticanisotropic energy can be performed. Furthermore, when the oscillationlayer 74 d of the spin-torque oscillator 74 is divided into theindependent oscillation regions, the generated high-frequency magneticfield of the spin-torque oscillator can be increased, the sufficientrecording capability can be exercised, and the stable recordingcharacteristics can be obtained. As a result, it is possible to obtainthe magnetic recording head that enables good recording with improvedrecording signal quality and the HDD provided with this magneticrecording head.

It is to be noted that the oscillation layer 74 d may be completelydivided by the slit 80 or the notch like the first embodiment, or a partof this layer may remain like a first modification depicted in FIG. 8A.That is, the slit 80 or the notch may be formed to be shallower than thefilm thickness of the oscillation layer 74 d. Moreover, like a secondmodification depicted in FIG. 8B, the slit 80 or the notch may be deeplyformed to divide a part of the intermediate layer 74 c. Like a thirdmodification depicted in FIG. 8C, the slit 80 or the notch may befurther deeply formed so that it pierces through the oscillation layer74 d and the intermediate layer 74 c to reach the spin injection layer74 b. In this case, the intermediate layer 74 c is also completelydivided.

Like a fourth modification depicted in FIG. 9A, the slit 80 or the notchmay be formed to pierce through the oscillation layer 74 d, theintermediate layer 74 c, and the spin injection layer 74 b. In thiscase, the oscillation layer 74 d, the intermediate layer 74 c, and thespin injection layer 74 b are completely divided into pieces by the slit80, respectively.

Like a fifth modification shown in FIG. 9B, the oscillation layer 74 dis not restricted to the two regions, and it may be divided into threeor more oscillation regions by slits or notches. Like a sixthmodification shown in FIG. 9C, the oscillation layer 74 d, theintermediate layer 74 c, and the spin injection layer 74 b may belaminated from the main pole 66 side in the mentioned order. In thiscase, a distance between the main pole 66 and the oscillation layer 74 dis reduced, and the range where a recording magnetic field generated bythe main pole 66 and a high-frequency magnetic field produced by theoscillation layer are efficiently superimposed is widened on the medium,thereby enabling good recording.

It is to be noted that, as illustrated in the first embodiment and thefirst, second, fifth, and sixth modifications, when the spin injectionlayer 74 b is configured to remain as a complete layer without beingdivided, a reaction involved by the oscillation of the oscillation layer74 d can suppress the oscillation of the spin injection layer 74 b andthe oscillation layer 74 d can be more stably oscillated.

In regard to a film thickness of the divided portion, i.e., a depth ofthe slit 80 or the notch in the above-described various kinds ofspin-torque oscillators, a coupling constant of spin waves in thedivided oscillation regions is obtained, and the obtained constantrepresents the film thickness of the oscillation layer in the dividedportion.

It is assumed that an amplitude of magnetization of a magnetic materialchanges with time as follows:

m=m ₀×exp(−t/τ)

When a relaxation time τ of the amplitude of the magnetic material isobtained based on Gilbert formula, the following expression can beobtained as rough approximation:

τ=1/α ω

Here, α is a damping constant, and ω is a resonant angular velocity (areference literature: Basics of Magnetic Engineering II, P 342, KeizoOhta, KYORITSU SHUPPAN Co., Ltd.).

When this expression is applied to the spin wave to obtain a relaxationlength λ₀ of the spin wave which is obtained as a product of therelaxation time and a group velocity, the following expression can beacquired:

$\begin{matrix}{\lambda_{0} = {{2/\alpha}\; k}} \\{= {\lambda/({\alpha\pi})}}\end{matrix}\quad$

where k is a wave number of the spin wave, and λ is a wavelength of thespin wave.

When this expression is applied to the spin wave to obtain a couplingconstant of the spin wave in each of the oscillation regions of theoscillation layer, the coupling constant C is represented as follows:

$\begin{matrix}{C = {{Ms}_{1}{t/{MsT}^{\exp {({{- l}/\lambda_{0}})}}}}} \\{= {{Ms}_{1}{t/{MsT}^{\exp {({{- {\alpha\pi}}\; {l/\lambda}})}}}}}\end{matrix}\quad$

That is, this expression represents that the spin wave generated in theoscillation layer in the one undivided portion is damped when passingthrough the oscillation layer in the divided portion and the amplitudeof the spin wave is reduced when the spin wave flows into theoscillation layer in the other undivided portion. Here, T is a filmthickness of the oscillation layer in the undivided portion, Ms issaturated magnetization in the undivided portion, t is a film thicknessof the oscillation layer in the divided portion, Ms1 is saturatedmagnetization in the divided portion, and l is a length of theoscillation layer in the divided portion.

Now, taking into account a situation that a wavelength of the spin waveto consider is in the same range as the element size and corresponds tothe damping constant α to approximately 0.01, the wavelength is αII/k to0. Therefore, in the above case, the coupling constant C is as followslike the rough approximation:

C=Ms ₁ t/MsT

That is, when the spin wave in the one undivided oscillation layer istransferred to the other divided oscillation layer, the amplitude isreduced to C=t/T.

It is known that energy loss of the spin wave is proportionate to asquare of the amplitude. Energy injection using spin torque isproportionate to a driving current of the spin-torque oscillator. Ingeneral, a variation in driving current required for oscillation isapproximately 20%, and an increase/decrease of 20% can be included inthe range of the variation. Therefore, it is desirable to include theenergy loss of the spin wave due to presence of the oscillation layer inthe divided portion into the range of 20%. When the saturatedmagnetization of the oscillation layer in the divided portion issubstantially equal to the saturated magnetization of the oscillationlayer in the undivided portion, it is preferable to set the amplitude ofthe spin wave to 40% or below. That is, it is desirable to set the filmthickness t of the divided portion to 45% or below of the film thicknessT of the undivided portion.

It is to be noted that, likewise, when the saturated magnetization ofthe oscillation layer in the divided portion is substantially equal tothe saturated magnetization of the oscillation layer in the undividedportion and the variation in driving current required for oscillation isapproximately 10%, it is desirable to set a ratio of the film thicknesst of the divided portion and the film thickness T of the undividedportion to 32% or below. Furthermore, when the variation in drivingcurrent required for oscillation is approximately 30%, it is preferableto set a ratio of the film thicknesses to 63% or below.

Like a seventh modification shown in FIG. 10, the oscillation layer 74 dmay be divided into pieces by an inactive region 84 in place of the slitor the notch. That is, ions of, e.g., N2, phosphorous, or helium may beimplanted into the oscillation layer 74 d from one surface side thereofby using a mask to deactivate magnetization of portions other than themask portion. The strip-like inactive region 84 deactivated byimplantation of the ions is provided, and the oscillation layer 74 d isdivided into a plurality of, e.g., two oscillation regions 82 a and 82 bon upper and lower sides by this inactive region 84. The shape of theinactive region 84 is not restricted to the strip-like shape, and a bentor crossed shape may be adopted.

When the inactive region 84 is used, the film thickness of theoscillation layer 74 d in the divided portion is equal to the filmthickness of the oscillation layer in the undivided portion, and thesaturated magnetization Ms is lowered. In this case, when the variationin driving current required for oscillation is approximately 20%, it isdesirable to set a ratio of the saturated magnetization Ms1 in thedivided portion and the saturated magnetization Ms in the undividedportion to 45% or below.

A description will now be given as to a magnetic recording head of anHDD according to another embodiment. It is to be noted that, in anotherembodiment described below, like reference numerals denote parts equalto those in the first embodiment to omit a detailed description thereof,and parts different from those of the first embodiment will be mainlyexplained in detail.

Second Embodiment

FIG. 11 schematically shows a recording head in a magnetic head of anHDD according to a second embodiment. According to this embodiment,oscillation regions 82 a and 82 b of an oscillation layer 74 d in aspin-torque oscillator 74 are aligned to interpose a gap in a directionof a track width of a main pole 66. For example, a slit 80 (or a notch)having a depth equal to a film thickness of the oscillation layer 74 dis formed at a substantially central part of the oscillation layer 74 d,and this slit 80 extends in a direction perpendicular to a surface of amagnetic disk 12. The oscillation layer 74 d is divided by this slit 80into the two oscillation regions 82 a and 82 b which are aligned in adirection parallel to the surface of the magnetic disk 12 to interpose agap therebetween.

The slit 80 or the notch is formed by forming the oscillation layer 74 dand then performing etching to remove the oscillation layer from thesurface side of the oscillation layer based on, e.g., ion milling orRIE. The slit 80 or the notch is filled with, e.g., a cap layer 74 eafter formation.

When the oscillation layer 74 d in the spin-torque oscillator 74 isdivided into the oscillation regions in this manner, the spin-torqueoscillator 74 can oscillate with a lower driving voltage, and it canoscillate with a large amplitude, thereby increasing a generatedhigh-frequency magnetic field. When the sufficient high-frequencymagnetic field is generated, the sufficient recording capability can beexercised, and stable recording characteristics can be realized.

FIG. 12 shows a relationship between circularly-polarized high-frequencymagnetic field intensity (c-Hac) generated from the spin-torqueoscillator and a shape and a dimension of the spin-torque oscillator.When the spin-torque oscillator 74 having an element size of 50 nm×50 nmis created, c-Hac of 410 (Oe) can be produced if excellent oscillationis carried out, but oscillation of just 180 (Oe) is actually performed.Further, since an element having an element size of 50 nm×17 nm is smallin element size, the excitation of a spin wave is suppressed, and hencethe oscillation becomes excellent. However, since the element size issmall, the generated c-Hac is just 290 (Oe).

In this embodiment, since the oscillation layer 74 d is divided into theoscillation regions 82 a and 82 b, it is equivalent to a configurationhaving two elements each having a size of 50 nm×17 nm on left and rightsides, and the generated c-Hac becomes 330 (Oe) as shown in FIG. 12.Therefore, according to this embodiment, it can be understood that anoscillation amplitude of the oscillation layer 74 d can be increasedwith a lower driving voltage and the circularly-polarized high-frequencymagnetic field intensity generated from the spin-torque oscillator 74 israised. As a result, good high-frequency assist recording is enabled.

Third Embodiment

FIG. 13 schematically shows a recording head in a magnetic head of anHDD according to a third embodiment. According to this embodiment, anoscillation layer 74 d of a spin-torque oscillator 74 is divided intothree or more independent oscillation regions 82 a, 82 b, 82 c, and 82d. Here, the oscillation regions 82 a, 82 b, 82 c, and 82 d of theoscillation layer 74 d are aligned in a direction perpendicular to asurface of the magnetic disk and a direction parallel to the samesurface at random intervals. For example, a slit 80 (or a notch) havinga depth equal to a film thickness of the oscillation layer 74 d isformed to cut across the oscillation layer 74 d in directions, and theoscillation layer 74 d is divided into the four oscillation regions 82a, 82 b, 82 c, and 82 d by this slit 80.

FIG. 14 shows a mask 86 for forming the slit 80 in the oscillation layer74 d. As this mask 86, a mask utilizing a self-assembled material can beused. It is possible to use the self-assembled material of an organicmatter such as PS—BS or an inorganic matter such as Al—Si. When dividingthe oscillation layer 74 d into the oscillation regions, etching may beperformed to remove a magnetic material by, e.g., ion milling using themask 86 or RIE, or ions of, e.g., N2, phosphorous, or helium may beimplanted by using this mask to deactivate magnetic properties inportions other than the mask portion.

When the oscillation layer 74 d of the spin-torque oscillator 74 isdivided into the oscillation regions in this manner, the spin-torqueoscillator 74 can oscillate with a lower driving voltage, and it canoscillate with a large amplitude, thereby increasing a generatedhigh-frequency magnetic field. When the sufficient high-frequencymagnetic field is generated, the sufficient recording capability can beexercised, and stable recording characteristics can be realized.

According to the above-described various embodiments and modifications,there can be provided the magnetic recording head that can increase thegenerated high-frequency magnetic field, exercise the sufficientrecording capability, and realize the stable recording characteristicsand the disk drive provided with this magnetic recording head.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1. A magnetic recording head comprising: a main pole configured to applya recording magnetic field to a recording layer of a recording medium; atrailing shield opposed to the main pole with a write gap between themain pole and the trailing shield; and a high-frequency oscillatorbetween the main pole and the trailing shield in a range of a width ofthe main pole in a track width direction, the high-frequency oscillatorconfigured to generate a high-frequency magnetic field, wherein thehigh-frequency oscillator comprises a spin injection layer, anintermediate layer, and an oscillation layer, and at least theoscillation layer comprises divided oscillation regions.
 2. The magneticrecording head of claim 1, wherein the oscillation regions of theoscillation layer are aligned in a direction perpendicular to a surfaceof the recording medium with a gap between the oscillation regions. 3.The magnetic recording head of claim 1, wherein the oscillation regionsof the oscillation layer are aligned in the track width direction of themain pole with a gap between the oscillation regions.
 4. The magneticrecording head of claim 1, wherein the oscillation regions of theoscillation layer are aligned in a direction perpendicular to a surfaceof the recording medium and in a direction parallel to the surface ofthe recording medium with gaps between the oscillation regions.
 5. Themagnetic recording head of claim 1, wherein the high-frequencyoscillator comprises a slit or a notch formed in at least one surface ofthe oscillation layer, and the oscillation regions are defined by theslit or notch.
 6. The magnetic recording head of claim 5, wherein theslit or the notch is formed to pierce the oscillation layer and reachthe intermediate layer.
 7. The magnetic recording head of claim 5,wherein the slit or the notch is formed to pierce the oscillation layerand the intermediate layer and reach the spin injection layer.
 8. Themagnetic recording head of claim 5, wherein the slit or the notch isformed to pierce the oscillation layer, the intermediate layer, and thespin injection layer.
 9. The magnetic recording head of claim 1, whereinthe oscillation layer comprises an inactive region, and the oscillationregions are divided by the inactive region.
 10. The magnetic recordinghead of claim 2, wherein the high-frequency oscillator comprises a slitor a notch formed in at least one surface of the oscillation layer, andthe oscillation regions are defined by the slit or notch.
 11. Themagnetic recording head of claim 10, wherein the slit or the notch isformed to pierce the oscillation layer and reach the intermediate layer.12. The magnetic recording head of claim 10, wherein the slit or thenotch is formed to pierce the oscillation layer and the intermediatelayer and reach the spin injection layer.
 13. The magnetic recordinghead of claim 10, wherein the slit or the notch is formed to pierce theoscillation layer, the intermediate layer, and the spin injection layer.14. The magnetic recording head of claim 2, wherein the oscillationlayer comprises an inactive region, and the oscillation regions aredivided by the inactive region.
 15. A disk drive comprising: adisk-shaped recording medium comprising a recording layer, the recordinglayer comprising magnetic anisotropy in a direction perpendicular to amedium surface; a driver configured to rotate the disk-shaped recordingmedium; and a magnetic recording head configured to perform informationprocessing with respect to the disk-shaped recording medium, themagnetic recording head comprising: a main pole configured to apply arecording magnetic field to the recording layer of the disk-shapedrecording medium; a trailing shield opposed to the main pole with awrite gap between the main pole and the trailing shield; and ahigh-frequency oscillator between the main pole and the trailing shieldin a range of a width of the main pole in a track width direction, thehigh-frequency oscillator configured to generate a high-frequencymagnetic field, wherein the high-frequency oscillator comprises a spininjection layer, an intermediate layer, and an oscillation layer, and atleast the oscillation layer comprises divided oscillation regions. 16.The disk drive of claim 15, wherein the oscillation regions of theoscillation layer are aligned in the direction perpendicular to asurface of the recording medium with a gap between the oscillationregions.
 17. The disk drive of claim 15, wherein the oscillation regionsof the oscillation layer are aligned in the track width direction of themain pole with a gap between the oscillation regions.
 18. The disk driveof claim 15, wherein the oscillation regions of the oscillation layerare aligned in the direction perpendicular to a surface of the recordingmedium and in a direction parallel to the surface of the recordingmedium with gaps between the oscillation regions.
 19. The disk drive ofclaim 15, wherein the high-frequency oscillator comprises a slit or anotch formed in at least one surface of the oscillation layer, and theoscillation regions are defined by the slit or notch.